Charakterisierung von Tumor-infiltrierenden Lymphozyten des Ovarialkarzinoms und die Entwicklung einer peptid-basierten Krebsimpfung

This thesis is about the characterization of tumor-infiltrating lymphocytes (TILs) and the development of a therapeutic peptide-based anti-cancer vaccine against ovarian cancer. The thesis is divided into three parts. The first part is about tumor-infiltrating lymphocytes and their expression of co-inhibitory and co-stimulatory receptors on the cell surface. For a more precise differentiation CD8+ cytotoxic T cells were separated from CD4+ T cells and the latter were further differentiated into regulatory T cells and T-helper cells. The co-inhibitory and co-stimulatory receptors CD137, cytotoxic T lymphocyte protein (CTLA-4), lymphocyte activation gene 3 (LAG 3), programmed cell death protein 1 (PD-1) und T cell immunoglobuline (TIM-3) were analyzed separately in the three different groups of regulatory T cells, cytotoxic T cells and T-helper cells. To evaluate the expression levels of the co-receptors on tumor-infiltrating lymphocytes, they were compared to lymphocytes from the peripheral blood (PBMCs) of each patient and PBMCs from healthy donors. It was shown that most of the receptors remained absent or of low expression besides PD-1 that apparently plays a dominant role in the immunosuppressive tumor microenvironment. Besides PD-1, CD137 shows low to moderate expression across the different patients being an interesting target for immunotherapy. The second part focusses on the isolation of natural HLA ligands from ovarian tumor tissue. The eluted peptides and their respective source proteins were compared to source proteins and their peptides of benign ovarian tissue and a database that contains autopsies of different benign tissues. Through comparative profiling tumor-exclusive source proteins were determined. At the end of the thesis these naturally presented tumor-exclusive ligands were used to treat patients who have no further therapy options. The treatment was able to induce HLA class I and HLA class II mediated reactions. The reactions were monitored through the course of therapy via IFN-γ ELISpot. Overall three patients were analyzed. In the first patient treated, we were able to induce a HLA class II mediate immune response. We were able to induce an HLA class I and II mediated immune response. The third patient has shown a pre-existing immune response against one HLA class I peptide and an immune reaction was induced against three HLA class II restricted peptides

The immunopeptidomic landscape of ovarian carcinomas

Immunotherapies, particularly checkpoint inhibitors, have set off a revolution in cancer therapy by releasing the power of the immune system. However, only little is known about the antigens that are essentially presented on cancer cells, capable of exposing them to immune cells. Large-scale HLA ligandome analysis has enabled us to exhaustively characterize the immunopeptidomic landscape of epithelial ovarian cancers (EOCs). Additional comparative profiling with the immunopeptidome of a variety of benign sources has unveiled a multitude of ovarian cancer antigens (MUC16, MSLN, LGALS1, IDO1, KLK10) to be presented by HLA class I and class II molecules exclusively on ovarian cancer cells. Most strikingly, ligands derived from mucin 16 and mesothelin, a molecular axis of prognostic importance in EOC, are prominent in a majority of patients. Differential gene-expression analysis has allowed us to confirm the relevance of these targets for EOC and further provided important insights into the relationship between gene transcript levels and HLA ligand presentation